1. Field of the Invention
The present invention relates to tunneling machines, and particularly to a new shielded tunneling machine incorporating an excavator and conveyor constructed as a unit.
2. Description of the Prior Art
Since the days in which tunnels were dug by hand with a pick and shovel, numerous types of machines have been developed in an attempt to more efficiently excavate tunnels. Powered jack hammers and shovels, such as disclosed in McDowell U.S. Pat. No. 1,100,142, have been utilized to more quickly loosen the earth at the tunnel face. Also, conveyors have been employed to more rapidly load the loosened materials at the tunnel face onto cars for removal rearwardly through the tunnel.
More recently, sophisticated tunneling and mining machinery has been developed. Forwardly extending booms having powered excavating tools at their front ends for excavating material at the tunnel face and an endless belt type conveyor for loading such loosened materials onto mine cars have been mounted on a single mobile vehicle. Generally, such a vehicle is self-propelled and rides either on tracks or ground engaging wheels. Examples of tunneling machines of this type are disclosed by Graham U.S. Pat. No. Re. 24,479; Gelfgren et al U.S. Pat. No. 3,726,382; Nakashima U.S. Pat. No. 3,958,831; Jenkins et al U.S. Pat. No. 3,978,675; and Beckmann at page 120.
On larger, less mobile vehicles rather than moving the entire chassis when digging at a tunnel face, the excavating portion of the machine has been adapted to move in the fore-and-aft direction relative to both the vehicle and the conveyor. Hoar U.S. Pat. No. 1,162,607, Shimada et al. U.S. Pat. No. 3,574,405 and Silvestro et al. U.S. Pat. No. 3,675,433 all disclose such types of tunneling machines. In all of these patents, an excavator is mounted on a carriage which is in turn supported by a vehicle frame for longitudinal movement within a tunnel.
If the ground material through which the tunnel is being formed is loose or contains a large amount of moisture, a shielded tunneling machine, rather than the unshielded types described above, may be required. In general, a shielded tunneling machine is capable of digging a tunnel which is more uniform in cross section and thus easier to line than a tunnel dug with an unshielded machine. Powered tunneling shields are usually constructed in two longitudinally aligned halves interconnected by powerful hydraulic rams arranged in a ring about the inside diameter of the two halves. These shields are propelled by initially extending the rams to push the front half of the shield forwardly into the tunnel face. After the rams have reached their full extension, they are retracted to pull the rear half of the shield forwardly into abutment with the shield front half to complete the stepwise movement. Examples of powered tunneling shields are disclosed by McDowell U.S. Pat. No. 1,100,142; Parker U.S. Pat. No. 2,111,405; Tabor U.S. Pat. Nos. 3,382,002, 3,404,535 and 3,404,920; Hayes U.S. Pat. No. 3,427,813; Fikse U.S. Pat. No. 3,556,599; Cunningham U.S. Pat. No. 3,578,809; Reuls U.S. Pat. No. 3,612,609; Jutte et al. U.S. Pat. No. 4,043,137; and Fritz U.S. Pat. No. 4,055,959.
Conveyors have been added to powered tunneling shields to transport the loosened ground material rearwardly through the tunnel. Examples of this type of tunneling machine are disclosed by the above mentioned Tabor '535, and Hayes '813 patents. If the spoil at the tunnel face is firmly packed, the tunneling shield by itself may not be capable of removing it and thus the spoil may have to be cut away with an additional apparatus such as a powered shovel, pick or rotary cutter. Examples of types of tunneling machines incorporating a powered shovel are disclosed by the afore noted McDowell '142 and Tabor '920 patents. The above discussed '599 and '809 patents to Fikse and Cunningham, respectively, disclose types of shielded tunnel machines utilizing powered picks. In addition, the previously noted Jutte et al '137 patent involve a type of shielded tunneling machine constructed with two powered rotary cutters.
Rather than utilizing a separate conveyor and powered excavating device, shielded tunneling machines have also employed a mobile vehicle on which both a conveyor and powered excavating apparatus have been mounted. Generally the digging or cutting tool is mounted on the front end portion of a forwardly extending boom which is pivotally supported by the vehicle. Examples of such tunneling machines are disclosed by the Parker '405 and Reuls '609 patents.
Shielded tunneling machines have also been constructed with powered excavators which are mounted on the shield itself for movement therewith. In this type of structure, the reaction forces created by the excavating tool as it loosens material at a tunneling face is carried by the entire shield rather than just by a mobile vehicle. Thus, relatively large excavating tools can be utilized to more quickly cut away the tunnel face. In general, this type of tunneling machine includes a carriage which is suspended downwardly from overhead tracks or rails for fore-and-aft movement relative to the shield. A boom having a bucket or other type of excavating tool mounted to its front end is pivotally connected to the carriage for travel therewith. Examples of such tunneling machines are disclosed by the Tabor '920 patent wherein a bucket type excavator empties muck into mine cars; the Fikse '599 patent wherein an excavating tool includes a blade portion for hoeing the spoil onto a conveyor; and the Jutte et all '137 patent wherein a cutter support boom is constructed with an integral conveyor for transporting mined materials back to a second or rear conveyor.
The Cunningham '809 patent discloses a similar tunneling machine wherein an excavator tool support boom is suspended from the ceiling of a powered tunneling shield by a four-bar link mechanism. To permit the excavating tool to move transversely about the tunneling face, the four-bar link mechanism is adapted to pivot about a vertical axis.
A major drawback of shielded tunneling machines, especially those incorporating an excavating device mounted directly to the shield, is that considerable time and expense is incurred during the preliminary stages of a tunneling project even before the machine can be used to dig a tunnel in its designed manner. Tunnels are usually begun by first digging a vertical hole down to the level corresponding to the elevation of the desired tunnel. Next the shield portion of the tunneling machine is lowered into the vertical hole and aligned with the direction of the desired tunnel. Using the rear wall of the vertical hole as a backstop, the shield is extended forwardly in its normal manner while the tunnel face is cut away either manually or through the use of a powered portable cutting device. Once the shield is buried, the remainder of the tunneling machine must then be assembled within the shield. The dark, dusty, and cramped quarters within the shield are not ideal conditions under which to assemble complicated, heavy machinery piece by piece. As a result, this procedure takes a great deal of time and often the tunneling machine is improperly assembled. Consequently, the machine often must be later required or reassembled, which is an expensive and time-consuming operation.